Ross,
OK, make sure that the TIU is powered on and do this:
- Press Menu/System/TIU Setup/Add TIU and highlight #3. Press the thumbwheel to add it
- Press Menu/System/TIU Setup/Delete TIU and select #1. Press the thumbwheel once to delete it and again to confirm
- Press Menu/TIU Setup/Edit TIU and select TIU #3. Press the thumbwheel and then select #1. Press the thumbwheel again to change the TIU's address to #1.
That should get you squared away.